1. Technical Field
Cross-linking polymers for organic anti-reflective coatings are disclosed that are able to improve the uniformity of a photoresist pattern having an ultra-fine pattern by photolithography with an ArF light source at a 194 nm wavelength. Organic anti-reflective coatings including the same and methods for forming a photoresist pattern using the same are also disclosed. More particularly, the disclosed cross-linking polymers make the organic anti-reflective coatings easy to remove, which prevents scattered reflection from the bottom film layer, they improve the uniformity of the thickness of the photoresist film and they eliminate the standing wave effect due to variations in the thickness of the photoresist film. At the same time, the disclosed cross-linking polymers increase the etching velocity of the organic anti-reflective coating thereby allowing the anti-reflective coating to be easily removed.
2. Description of the Related Art
In semiconductor production processes, an ultra-fine pattern formation process (hereinafter abbreviated as “the patterning method”) necessarily involves standing waves in the photoresist film caused by variations of the optical properties of a bottom film layer and/or variations in the thickness of the photoresist film formed on the top portion of the bottom film layer. Other effects of the patterning method include reflective notching status and variation of critical dimension (hereinafter referred to as CD) of patterns of the photoresist induced by diffracted light and reflected light from the bottom film layer.
To address these problems, an intermediate film has been proposed in the form of a so-called anti-reflective coating, which can prevent diffused light reflection in the bottom film layer. The anti-reflection coating can be prepared by introducing a material having a higher light absorption in the bandwidth for the exposure light source. The anti-reflective coating is located between the bottom film layer and the photoresist. Such an anti-reflective film is generally divided into inorganic anti-reflective coatings and organic anti-reflective coatings, depending upon the different materials used in the coatings.
In recent years, organic anti-reflective coatings are applied in the ultra-fine pattern formation process and, thus, needs to satisfy the following requirements:
(1) After depositing the organic anti-reflective coating and coating a photoresist film on top portion thereof, the anti-reflective coating should resist being dissolved in the solvent for the photoresist. To accomplish this, the anti-reflective coating should have cross-linking structures. The cross-linking structures can be created during the lamination process which is followed by a baking process which inhibits the generation of other chemical materials as side products.
(2) In order to prevent scattered reflection from bottom film layer, the anti-reflective coating should contain certain materials to absorb light at the wavelength range of the exposure light source; and
(3) Finally, the anti-reflective needs a catalyst to activate such cross-linking reaction in a process for laminating the anti-reflective coating composition.
In order to achieve these requirements, conventional organic anti-reflective coatings generally included a cross-linking agent to allow the anti-reflective coating to have a cross-linkage structure, a light absorbent agent to absorb the light at the wavelength range of exposure light source, and a thermal acid generator as a catalyst for activating the cross-linking reaction.
With respect to the ultra-fine pattern formation process of the photoresist using ArF light source with a 193 nm wavelength, a process has been proposed for producing an organic anti-reflective coating on bottom portion of a photoresist film that includes polyvinylphenol represented by the following Formula 1 as a light absorbent agent and, a polymer represented by the following Formula 2 wherein each of R1 and R2 is methyl group and R3 is hydrogen as described in the document, Polymer 41 (2000) 6691–6694.

Using polyvinylphenol as the light absorbent agent in a conventional organic anti-reflective coating composition shows a higher absorbance to ArF light source having a 193 nm wavelength. The resulting coating can remove reflected light and standing wave on the bottom film layer and have cross-linkage bonds within the organic anti-reflective coating as well as the cross-linking agent represented by the above Formula 2.
However, when the anti-reflective coating was produced by using the conventional organic anti-reflective coating, a problem was found in that the composition showed a lower etching velocity which prevented removal of the anti-reflective coating under normal etching conditions. Due to such a low etching rate and velocity, an over-etching process was required to remove the anti-reflective coating which caused damage to the bottom film layer, thereby adversely affecting the reliability of the final product.
Accordingly, a strong demand exists for a novel organic anti-reflective coating and a composition of the same that can efficiently eliminate scattered reflection and standing waves in bottom film layer and, which also have an etching velocity and etching rate sufficient so that the coating can be easily removed under normal etching conditions.